The present technique relates to a storage apparatus and a storage control circuitry for reading/writing data by causing a head to fly above a rotating storage medium. The present technique pertains to a storage apparatus and storage control circuitry capable of appropriately addressing the reduction in clearance between the head and a storage medium under an environment of reduced atmospheric pressure.
In order to realize a high recording density of a magnetic disk device, to reduce the clearance (spacing) between an element part of the head and a recording surface of the magnetic disk is necessary. Hence, the clearance generated by the flying of the head above the storage medium has been designed to be constant by taking advantage of the pressure of air (positive pressure/negative pressure) flowing between a slider having the magnetic head and the magnetic recording medium.
In order to enhance the recording density, the distance between the head and the medium must be reduced. Hence, the clearance between the head and the medium has been decreased with a tendency toward a higher recording density. Eventually the clearance has been reduced down to several nm, by controlling the clearance between the head and the recording medium surface utilizing thermal expansion accompanying electric heating of a heater provided to the head.
In such a method in which the clearance between the head and the magnetic recording surface is controlled by providing the heater to the head, there is no problem as long as under a normal usage environment. However, once the magnetic disk has been installed in an environment of reduced atmospheric pressure, for example, installed at a highland, the clearance may decrease to thereby bring the head and magnetic disk into contact. As a result, there occurs a possibility that data to be written may not correctly recorded into the magnetic disk, and hence that the data recorded in the magnetic disk cannot be correctly read.
In order to avoid such a failure under a usage environment of reduced atmospheric pressure, the design of the shape of a head floating surface or the setting of energization amount to the heater is performed so that the clearance becomes one in which the decrement in clearance due to atmospheric pressure decrease is added to the clearance under a normal atmospheric pressure (1 atm) beforehand in manufacturing process. With such a countermeasure used, however, the clearance under a normal atmospheric pressure, which is high in usage frequency, becomes too large, thereby causing a situation of increasing an error rate.
Techniques of the related art are disclosed in Japanese Laid-open Patent Publication No. 7-262726, Japanese Laid-open Patent Publication No. 2002-150744 and Japanese Laid-open Patent Publication No. 2006-107722.